arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2004.09129cs.DScs.DC
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近优时间的分布式加权最小割

Distributed Weighted Min-Cut in Nearly-Optimal Time

Michal Dory, Yuval Efron, Sagnik Mukhopadhyay, Danupon Nanongkai

摘要:

最小权割(min-cut)是网络连通性强度的基本度量。虽然在顺序设置中可以有效地计算最小割[Karger STOC'96],但对于分布式网络来说,没有有效的方法来计算自己的最小割而不限制输入结构或降低输出质量:在标准的CONGEST模型中,具有接近最优时间的现有算法(例如[Ghaffari,Kuhn,DISC'13; Nanongkai,Su,DISC'14])可以保证最好是$(1+ε)$近似的解,而精确的$\tilde O(n^{0.8}D^{0.2} + n^{0.9})$时间算法[Ghaffari,Nowicki,Thorup,SODA'20]仅适用于 * 简单 * 网络(没有权重和平行边)。这里$n$和$D$分别表示网络的顶点数和跳数直径。对于加权情况,最佳界限是$\tilde O(n)$ [Daga,Henzinger,Nanongkai,Saranurak,STOC'19]。本文给出了一个计算加权网络最小割的 * 精确 * $\tilde O(\sqrt n + D)$ -时间算法。我们的结果甚至改进了以前只适用于简单网络的算法。它的时间复杂度与已知的下限匹配到多对数因子。在我们的算法的核心是一个聪明的路由技巧和两个结构引理的最小割图的结构。这两个结构引理大大加强和推广了Mukhopadhyay-Nanongkai [STOC'20]的框架,并且可以是独立的。

英文摘要:

Minimum-weight cut (min-cut) is a basic measure of a network's connectivity strength. While the min-cut can be computed efficiently in the sequential setting [Karger STOC'96], there was no efficient way for a distributed network to compute its own min-cut without limiting the input structure or dropping the output quality: In the standard CONGEST model, existing algorithms with nearly-optimal time (e.g. [Ghaffari, Kuhn, DISC'13; Nanongkai, Su, DISC'14]) can guarantee a solution that is $(1+ε)$-approximation at best while the exact $\tilde O(n^{0.8}D^{0.2} + n^{0.9})$-time algorithm [Ghaffari, Nowicki, Thorup, SODA'20] works only on *simple* networks (no weights and no parallel edges). Here $n$ and $D$ denote the network's number of vertices and hop-diameter, respectively. For the weighted case, the best bound was $\tilde O(n)$ [Daga, Henzinger, Nanongkai, Saranurak, STOC'19]. In this paper, we provide an *exact* $\tilde O(\sqrt n + D)$-time algorithm for computing min-cut on *weighted* networks. Our result improves even the previous algorithm that works only on simple networks. Its time complexity matches the known lower bound up to polylogarithmic factors. At the heart of our algorithm are a clever routing trick and two structural lemmas regarding the structure of a minimum cut of a graph. These two structural lemmas considerably strengthen and generalize the framework of Mukhopadhyay-Nanongkai [STOC'20] and can be of independent interest.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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